Photo-mechanical correction of colours



Aug. 12, 1958 w. THIELE 2,847,307

` PHOTO-MECHANICAL CORRECTION OF COLOURS Filedcd'.. l, 1951 3 Sheets-Sheet l LIGHT SouQCE.

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PHOTO-MECHANICAL CORRECTION OF COLOURS Filed oct. 1, 1951 s sheets-sheet 2 d Erd/777i',

W. THIELE Aug. 12, 1958 PHOTO-MECHANICAL CORRECTION OF COLOURS 3 Sheets-Sheet 3 Filed Oct. l, 195] United States Patent O PHOTO-NLECHANICAL CORRECTION OF COLOURS The present invention relates to the photomechanical correction of colours, this application being a continuation in part of my application Serial No. 191,552, filed October 23', 1950, now abandoned.

The invention is concerned with the reproduction of coloured objects by a process inwhich a number, usually three, of separation negatives are produced with the aid of suitable filters, each negative being representative of a different colour in the object. In such a process it is known that imperfections occur owing amongst other things to the photographic emulsions employed not having 'a uniformsensitivity to all colours. In order to correct such imperfections it is known to carry out a process known as masking. For this a diapositive is produced from each separation negative and when each negative is printed on to its final emulsion, at least part of the light for such printing is transmitted through an appropriate 'one of the diapositives or through more than one of the diapositives in successive steps. The diapositives are known as masks and hitherto they have been made by contact printing as described in U. S. patent specifications Nos. 1,886,556 and 2,060,816. This known masking process isA very inexible and it is not generally possible to obtain adequate correction of the imperfections referred to Without re-touching by hand which is a highly skilled processl requiring much time.

- As ypointed out in my antecedent application Ser. No. 191,552 the reproduction of the coloured objects after thephotoprojective correction of the colours with which the invention is concerned, may be accomplished by any offthe known photographic or photomechanical multicolour printing processes; and where the latter are concerned, the impurities ofthe printing colours or inks employed for the superposed printing on paper of the three primary or component colours are amongst the things that contribute to colour imperfections, Athat can at least partially be compensated for by colour corrections inl accordance with the present invention.

The present invention has for its principal object to providea method of and apparatus for use in producing coloured pictures in which much greater flexibility is provided and in which, in consequence, the need for manual re-touching can be substantially reduced.

-According to the invention a method of making a coloured picture of an object in which the final picture is photographically produced comprises the steps of photographing the object to produce va plurality of separation negatives eachrepresentative of a different colour in the object, placing a first of said negatives in ay first plane in the path of light from a first source, placing a photosensitive emulsion in a second plane, forming an image of said negative with the aid of a lens and the light from said source upon said emulsion, removing and processing said emulsion to produce a diapositive, placing a second one of said negatives in said first plane in contact with a second'photosensitive emulsion, with theA second emulsion Lon the side of the second negative remote from the lens, placing said diapositive-.in said second plane,` form- 2,847,307 Patented Aug. 12, 1958 ing on said second emulsion with the aid of a second light source and said lens an image of said diapositive in register with the image on the second negative in order to print said second negative upon said second emulsion, printing each of the negatives other than said second negative in succession upon the second emulsion and processing the second emulsion to produce a coloured picture.

When the final picture is to be produced photomechanically by mechanical printing from photographically produced colour component plates, the colour separation negatives and diapositives are made by projection as aforesaid, and the respective colour separation negatives are printed as their own colour separation plates with diapositive correction asv usual exc'ep'ttfiat this printing is accomplished with light projected from the appropriate diapositives as aforesaid.

The invention also provides apparatus comprising a lens, a light-tight structure on each side of said lens, means to vsupport and to ensure accurate location of a photographic plate in each of said light-tight structures and in conjugate planes with respect to said lens and two light sources disposed respectively on the sides of said planes remote from said lens.

The invention will be described by way of example with reference to the accompanying drawings in which:

Figs. l, 2 and 3 are diagrams illustrating steps in the process according to the invention,

- Fig. 4 shows a plate holder provided with accurate locating means,

Figs. 5 and 6 are somewhat diagrammatic views in elevation and plan respectively of apparatus for carrying out the process exemplified by Figs. l to 3, and

Fig. 7 Vis a view in elevation of one embodiment of the apparatus of Figs. 5 and 6.

Referring to Figs. 1 to 3, plate holders are diagrammatically represented at 10 and 11 and each of these may be of the kind shown in Fig. 4 and to be described in more detail later. it forms the subject of my abovementioned application Serial No. 191,552 which gives a still fuller description of the holder. It serves to locate a photographic plate accurately in a desired position and enables the plate to be removed and returned to the same position.

- Making colour separation negatives In one form of the process according to the invention to be described, a colouredtransparency t of which a copy is to be made is arranged in the holder 10 with its emulsio-n e facing to the right. A sensitive plate P is arranged in the holder 11 with its emulsion e1 facing to the left. With the aid of a light source L1 and lens O an image of the transparency t is formed on P. A filter F is placed in the path of the light. The plate P1 is then removed and processed to produce a separation negative representative of the complementary colour to that transmitted by the filter F. Two other separation negatives P11 and P3, not shown, representative of other colours are then made in the same way using appropriate coloured filters at F.

Making diapositive masks A. photosensitive plate M1 is then arranged in the holder 10 as shown in Fig. 2 with its emulsion e2 facing to the right and the negative P1 is replaced in the holder 11 in a reversed position, that is with its emulsion e1 facing to the right and a clear glass plate A is inserted as a spacer between the plate P1 and the supporting surface of the holder 11. With the aid of a second light source L2 and the same lens O the plate M1 is suitably exposed to an image of the negative P1. Before this explosure the 'distances are .adjusted for sharp focusing and the l elements 10, 11 and O are then clamped and remain.

3 clamped in the sameposition during the remainder of the process. The plate M1 is removed and processed to form a diapositive mask. Other masks M2 and M3 not shown in Fig. 2 are produced in the same way from the negatives P2 and P3 respectively. The steps abovedescribed thus provide three colour separation negatives produced by projection, and three diapositives produced therefrom by projection, and usable in accordance with the present invention for producing corrected colour component exposures on sensitized surfaces, for example, those of the sensitized coloured picture plate when the final colour picture is to be reproduced photographically, as will now be described.

Making final 'prinz photographically The Vglass plateA of Fig. 2 is then replaced by a sensitive plate `B on which the final picture is to be produced and one of the negatives, say P1 is arranged withits emulsion surface e1 in contact with that of the plate B. An appropriate one of the masks, say M2, is then arranged in the holder With its emulsion surface e3 facing to the right and the plate B is exposed to the negative P1 by light from the source L1 passing through the mask M2 for a suitable time. If desired a further exposure of the plate B to the negative P1 may be made through another mask M2. A part of the exposure of the plate B to each negative such as P1 may of course be made without a mask in the holder 10.

The negative P1 is then replaced by the plates P2 and P3 in turn and the masking process is repeated using appropriate ones of the masks-for appropriate exposure times in each case. The plate B is then removed and processed to produce a coloured picture.

Making nal 'print photomechanz'cally As will be clear to those-skilled in the art from the foregoing, when the picture is to be reproduced in quantity'by photo-mechanical printing, the steps subsequent to the production of the diapositives, as described just above in connection with Fig. 3 are practiced in substantially the same way, using the sensitized printing plates at B with the appropriate colour separation negatives and diapositive masks at P1 and M2 respectively.

Other advantages Daal purpose mask .Instead of producing all the desired masking effects upon different masks, a number of effects can be produced upon a single mask. Thus for instance a colourcorrecting mask may be arranged to serve also for shadow correction by exposing the mask to a separation negative as already described and adjusting the exposure time to give the required characteristics or by carrying out part of the exposure through a diapositive having the required characteristics. Moreover a single mask may be exposed successively to more than one separation negative.

Locating means The preferred accurate locating means that may be used in the plate holders at 10 and 11 is shown in Fig. 4 and is described in more detail in my application Serial No. 191,552 already referred to. This comprises an outer frame 12 having a panel 13 with a central window indicated in broken lines 14. A platePis pressed against the `panel 13 by blade springs 15 and has one edgelocated against two lays 16 and 17 and an edge at right angles to the first-named edge located against a single lay 18. The plate is pressed against the lays by like spring devices 19 and 20, the device 20 being shown with its cover removed. The lays are preferably in the form of circularcylindrical pins. With such a locating device the plate can be removed andreplaced in exactly its previous position.

The outer frame 12 may be located with respect to the camera or container with which it is to be used by a like system of lays and spring devices `butas shown it is located by dowels, either carried bythe frame l12 or by the camera, engaging as a good tit in apertures in the other part. In'Fig. 4 dowels 21, 22 and 23 are used when the plate is oriented as shown with the longer dimension across the paper and dowels 24, 25 and 23 are used when the plate is oriented with the longer dimension up and down.

In Figs. 1 to 3the locating means are indicateddiagrammatically with references corresponding to those in Fig. 4

but with single and double prime supersc'ripts.

Apparatus Figs. 5 and 6 show diagrammatically in elevation and plan respectively and Fig. 7 shows in elevation appreferred apparatus for use in carrying out the process described. The light sources L1 and L2 areconstituted by lamps arranged in housings 26 and 27 respectively. The plate holder for the plate P1 in Fig. 1 is at 11 in Figs. 5 and 6 and the plate holder for the plate t in Fig. l is at 10' in Figs. 5 and 6. The lens O of Fig. 1 is carried in a lens tube 28 carried on a support 29 which is connected in a light-tight manner by a bellows 30 to a camera body 31 onwhich the plate holder .11 is mounted. What may be called the compendium camera comprises a bellows 32 connecting the lens tube 28 ina light-tight manner to .a compendium camera body 33 on which the plate holder 10 is mounted.

The parts 27 and 31 are mounted on a common support 34 and this support is adjustably mounted on a pair of rails 45 one of which is of V-shaped cross-section. The compendium camera body 33 is adjustably mounted on the same rails 45. The lens support 29 is adjustably mounted upon a second pair of rails 46, one of which is of V-shaped cross-section. The V-shape ensuresaccurate parallel movement. The rails 45 and 46 yand the lamp housing 26 are adjustably mounted on a further pair of rails 36 one of which is V-shaped. Suitable adjusting means including racks and adjusting screws are provided for adjusting the positions of these parts on the rails. Means are also provided for locking the parts rmly in position. Shock absorbing members 43 are interposed between the rails 36 and a supporting studl44.

For some purposes a condenser 37 is used with the light source. L1 and the lamp 38 is then used. yAlternatively thecondenser may be removed and diffused light from lamps 39 and 40 may then be used.

When a copy of a picture on paper rather than of a transparency (t in Fig. 1) is required, use may be made of a copy board 41 on which the picture is fixed. Light sources 42 serve to illuminate the picture.

I claim:

1. A method of making a corrected image of a color component of an object, that comprises: (a) making color separation negatives of an object in identical registry on plates identically positioned by mechanical positioning means contacting three predetermined points on said plates lying at the apices of a triangular pattern and processing said plates to produce a plurality of separation negatives each representing a different color in the object; (b) positioning a rst of said negatives in the first of two predetermined conjugate planes in a position predetermined by mechanical positioning means contacting the said'predetermined points on said negative and 1ocated at said first plane, positioning a first photosensitized plate in a predetermined restorable position in the second of said conjugate planes with the aid of like mechanical positioning means contacting three predetermined points on said plate lying at the apices of a triangular pattern and disposed at said second plane, photographing on said first plate the image of the object from said first negative with the aid of lens means disposed between said two planes and a first light source positioned adjacent the rst plane on the side thereof remote `from said lens means, removing said first negative, and removing and processing said first plate to produce a first diapositive mask, while leaving undisturbed the mechanical positioning means disposed at said first and second planes; (c) positioning a second of said negatives in said first plane in the position predetermined by said undisturbed mechanical positioning means thereat, positioning a second photosensitized plate in said second plane in the position predetermined by said mechanical positioning means thereat, photographing on said second plate with the aid of said lens means and said first light source the image of the object from said second negative, removing said second negative, and removing and processing said second photosensitized plate to produce a second diapositive mask, still leaving undisturbed the mechanical positioning means disposed at said first and second planes; (c) positioning a third of said negatives in said first plane in the position predetermined by said undisturbed mechanical positioning means thereat and disposing a third photosensitized plate on the side of said third negative remote from said lens means, replacing one of said disapositive masks in said second plane in the position predetermined by said undisturbed mechanical positioning means thereat, and photographing on said third plate the so mechanically registered images of the object from said third negative and from the so replaced mask with the aid of said lens means and a second light source positioned adjacent said second plane on the side thereof remote from said lens; (e) removing the last named mask from said second plane Without disturbing the mechanical positioning means disposed thereat and, without disturbing said third negative and said third sensitized plate placing the second of said diapositive masks in said second plane in the position predetermined by said undisturbed mechanical positioning means thereat, and photographing on said undisturbed third plate the so mechanically registered images of the object from said third negative and said last named mask with the aid of said lens and said second light source.

2. A method of making a corrected image of a color component of an object, that comprises: (a) making color separation negatives of an object in identical registry on plates identically positioned by mechanical positioning means contacting three predetermined points on said plates lying at the apices of a triangular pattern and processing said plates to produce a plurality of separation negatives each representing a difierent color in the object; (b) positioning a first of said negatives in the first of two predetermined conjugated planes in a position predetermined by mechanical positioning means contacting the said predetermined points on said negative and located at said first plane, positioning a first photosensitized plate in a predetermined restorable position in the second of said conjugate planes with the aid of like mechanical positioning means contacting three predetermined points on said plate lying at the apices of a triangular pattern and disposed at said second plane, photographing on said rst plate the image of the object from said rst negative with the aid of lens means disposed between said two planes and a first light source positioned adjacent the first plane at the side thereof remote from said lens means, removing said first negative, and removing and processing said first plate to produce a first diapositive mask, while leaving undisturbed the mechanical positioning means disposed at said first and second planes; (c) positioning one of said negatives other than said first negative in said first plane in the position predetermined by said undisturbed mechanical positioning means thereat and disposing a photosensitized plate other than said first photosensitized plate on the side of said other negative remote from said lens means, replacing said diapositive mask in said second plane in the position predetermined by said undisturbed mechanical positioning means thereat, and photographing on the last named sensitized plate the so mechanically registered images of the object from said other negative and from the so replaced mask with the aid of said lens means and a second light source positioned adjacent said second plane at the side thereof remote from said lens.

References Cited in the file of this patent UNITED STATES PATENTS 1,035,977 Lamb Aug. 20, 1912 1,373,020 Raschke Mar. 29, 1921 1,413,406 Huebner Apr. 18, 1922 1,739,886 Caps Dec. 17, 1929 1,944,561 Kronschnabl Jan. 23, 1934 2,004,144 Wilkinson June 11, 1935 2,060,816 Mackay Nov. 17, 1936 2,071,010 Weberling Feb. 16, 1937 2,099,916 Wilkinson Nov. 23,4 1937 2,177,195 Wilkinson Oct. 24, 1939 2,413,468 Rachett Dec. 31, 1946 2,420,636 Yule May 13, 1947 2,484,154 Wheldon Oct. 1l, 1949 2,466,154 Conklin Apr. 5, 1949 2,553,285 Thomas May 15, 1951 2,701,196 Conrad Feb. 1, 1955 

2. A METHOD OF MAKING A CORRECTED IMAGE OF A COLOR COMPONENT OF AN OBJECT, THAT COMPRISES: (A) MAKING COLOR SEPARATION NEGATIVES OF AN OBJECT IN IDENTICAL REGISTRY ON PLATES IDENTICALLY POSITIONED BY MECHANICAL POSITIONING MEANS CONTACTING THREE PREDETERMINED POINTS ON SAID PLATES LYING AT THE APICES OF A TRIANGULAR PATTERN AND PROCESSING SAID PLATES TO PRODUCE A PLURALITY OF SEPARATION NEGATIVES EACH REPRESENTING A DIFFERENT COLOR IN THE OBJECT, (B) POSITIONING A FIRST OF SAID NEGATIVES IN THE FIRST OF TWO PREDETERMINED CONJUGATED PLANES IN A POSITION PREDETERMINED BY MECHANICAL POSITIONING MEANS CONTACTING THE SAID PREDETERMINED POINTS ON SAID NEGATIVE AND LOCATED AT SAID FIRST PLANE, POSITIONING A FIRST PHOTOSENSITIZED PLATE IN A PREDETERMINED RESTORABLE POSITION IN THE SECOND OF SAID CONJUGATE PLANES WITH THE AID OF LIKE MECHANICAL POSITIONING MEANS CONTACTING THREE PREDETERMINED POINTS ON SAID PLATE LYING AT THE APICES OF A TRIANGULAR PATTERN AND DISPOSED AT SAID SECOND PLANE, PHOTOGRAPHING ON SAID FIRST PLATE THE IMAGE OF THE OBJECT FROM SAID FIRST NEGATIVE WITH THE ACID OF LENS MEANS DISPOSED BETWEEN SAID TWO PLANES AND A FIRST LIGHT SOURCE POSITIONED ADJACENT THE FIRST PLANE AT THE SIDE THEREOF REMOTE FROM SAID LENS MEANS, REMOVING SAID FIRST NEGATIVE, AND REMOVING AND PROCESSING SAID FIRST PLATE TO PRODUCE A 